Retrospective exposure assessment for carcinogenic agents in bitumen waterproofing industry in Finland and denmark

Our plain-English summary of Retrospective exposure assessment for carcinogenic agents in bitumen waterproofing industry in Finland and denmark, by P. Anttila, P. Heikkilä, M. Mäkelä, et al (The Annals of Occupational Hygiene, 2009).

The study

• Authors: P. Anttila, P. Heikkilä, M. Mäkelä, V. Schlünssen, E. Priha
• Journal: The Annals of Occupational Hygiene
• Published: 2009;53(2):139-51
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: The purpose of the study was (i) to identify the carcinogenic agents that may cause confounding when studying the exposure-response relationship between bitumen fume exposure and cancer among roofing membrane-manufacturing workers and roofers and (ii) to assess exposures to the identified carcinogens and bitumen fume in roofing membrane manufacturing and roofing in Finland and Denmark from 1950 to 2005.

Methods: Information on the use of carcinogenic agents and other relevant data were collected through semi-structured interviews of senior employees in the industry. Semi-quantitative exposure assessments were made on the basis of available measurement data and information obtained from the interviews and literature.

Results: Most of the production line workers in roofing membrane plants in Finland were exposed to asbestos until the mid-1970s. Also, some of the mixer operators in the plants were exposed to asbestos in Finland during the 1970s and in Denmark from the mid-1960s to the mid-1980s. In both countries, coal tar pitch was used in roofing membrane manufacturing until the mid-1960s, and consequently, exposure to polycyclic aromatic hydrocarbons (PAHs) in the plants was high in the 1950s and still significant in the early 1960s. Exposure of production line workers to quartz dust was high until the 1980s and is still relatively high compared with current occupational exposure limit values. Bitumen roofers' exposure to coal tar-derived PAHs may have been significant in both countries until the end of 1960s. Roofers' exposure to asbestos and quartz was estimated to have been near background level.

Conclusions: The estimated average annual exposures to asbestos, coal tar-derived PAHs and quartz dust in the bitumen waterproofing industry in Finland and Denmark were significant in the past but have a clear declining trend. Exposure to bitumen fume was found to follow a similar trend.

In plain English

This exposure assessment, not a study of disease, aimed to identify carcinogens besides bitumen fume and estimate past exposures in Finnish and Danish roofing membrane plants and roofing, 1950 to 2005. They interviewed 12 senior employees in Finland and 6 in Denmark and gathered air measurements. A panel of four industrial hygienists made semi-quantitative estimates. In Finland, asbestos surfaced membranes until the mid-1970s, and exposed production line workers' estimated mean annual exposure was high, above 0.5 fibres per cubic centimetre. Later, tremolite-contaminated talc gave low exposure, about 0.01 fibres per cubic centimetre. Mixer operators adding asbestos filler had estimated medium mean annual exposures of 0.1 to 0.5 fibres per cubic centimetre (Finland, 1970s; Denmark, mid-1960s to late 1970s). Roofers' asbestos exposure was estimated near background. In the plants, coal tar pitch exposure was estimated high in the 1950s, quartz dust very high until the mid-1980s and high afterwards. The authors concluded these exposures were significant in the past but have clearly declined. They noted that measurement data were sparse.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective, semi-quantitative exposure assessment based on interviews, documents and existing measurement data (not an epidemiological study of disease)
• Who was studied: Roofing membrane-manufacturing workers (production line workers and mixer operators) and bitumen roofers in Finland and Denmark, 1950 to 2005. Information came from interviews with 12 senior or retired employees in Finland (from three roofing membrane plants and the roofing field) and 6 in Denmark (from two plants and a small roofing company), plus a questionnaire sent to seven smaller Finnish roofing companies.
• Exposure: Asbestos was used as a roofing membrane surfacing material (Finland) and as a filler in coating bitumen (both countries). Talc containing tremolite asbestos as a contaminant was used for surfacing. Roofers met asbestos in demolition of asbestos-cement roofs and in asbestos-containing membranes. Bitumen fume, coal tar pitch volatiles (benzo[a]pyrene as indicator) and respirable quartz were also assessed. Formaldehyde, diesel exhaust and benzene were discussed.
• Main results:
  • Finnish production line workers exposed to asbestos: the mean annual exposure was estimated as high (above 0.5 fibres per cubic centimetre) until the mid-1970s, when asbestos was used as surfacing material. Asbestos-surfaced membranes made up 5 to 30% of production in plants that used it. Exposed workers spent an estimated 15% of working time exposed. Table 6 lists 70% of production line workers as exposed.
  • Finnish production line workers, mid-1970s to mid-1980s, when only talc contaminated with tremolite asbestos was used: estimated exposure was low, about 0.01 fibres per cubic centimetre.
  • Finnish mixer operators who added asbestos as a filler in the 1970s: the mean annual exposure was estimated as medium (0.1 to 0.5 fibres per cubic centimetre). Sparse measurements showed about 2 fibres per cubic centimetre during the adding of asbestos itself.
  • Danish mixer operators: estimated medium mean annual exposure (0.1 to 0.5 fibres per cubic centimetre) from the mid-1960s to the late 1970s. It fell to low (0.01 to 0.1) in the early 1980s and ceased in the mid-1980s.
  • Danish production line workers: estimated low asbestos exposure (0.01 to 0.1 fibres per cubic centimetre) from the mid-1960s to the mid-1980s, from talc surfacing. The talc's asbestos content was not known, so the content of Swedish talc used in Finland was used as the estimate.
  • Finnish bitumen roofers: careful demolition of asbestos-cement roofs gave about 0.1 fibres per cubic centimetre. Because contact with asbestos products was only a few percent of working time, the mean annual exposure was estimated below 0.01 fibres per cubic centimetre from the 1950s to the 2000s.
  • Danish bitumen roofers: the mean annual asbestos exposure was estimated to be near background level from the 1950s to the 2000s.
  • Coal tar pitch was used in membrane manufacturing in Finland until the mid-1960s (in Denmark until 1967). Estimated benzo[a]pyrene exposure of production line workers was high in the 1950s (Table 9). These estimates rested mainly on US data.
  • Production line workers' respirable quartz dust exposure was estimated as very high (above 0.5 mg per cubic metre) until the mid-1980s.
  • From the mid-1980s, quartz exposure was 0.1 to 0.5 mg per cubic metre, rated 'high' in Table 11 through 2005. The authors stated that levels are still high compared with current occupational exposure limits. The Finnish measurement method gives values about twice those of the common cyclone method. Danish levels were estimated to be the same as Finland's.
  • In the discussion, the authors cited four diagnosed cases of occupational asbestos disease among Finnish roofing membrane-manufacturing workers in 1993 to 2002, recorded in the Finnish Register of Occupational Diseases. They took these as confirming significant past asbestos exposure in the plants.
• The authors' conclusion: The authors concluded that estimated average annual exposures to asbestos, coal tar-derived PAHs and quartz dust in the bitumen waterproofing industry in Finland and Denmark were significant in the past but show a clear declining trend. They also concluded that bitumen fume exposure followed a similar trend.
• Limitations the authors state:
  • It is not known how representative the companies studied are, and plants that had already closed could not be checked.
  • Exposure measurement data were sparse in both countries.
  • The purpose of many workplace air measurements was unknown, so some results may not represent actual exposure.
  • No measurements of asbestos during asbestos surfacing were available. The 5 fibres per cubic centimetre estimate was based on data from other industries.
  • Coal tar pitch exposure estimates were based mainly on sparse US data.
  • Skin and hand-to-mouth exposure to PAHs could not be evaluated.

Topics

Medical terms in this study, explained in our Lexicon: Carcinogenic, Confounding, Occupational Exposure.

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